Comment 1 for bug 1617765

Trying again some minutes later, this is now working; I dont know how worrying this, please close if you think this is not worth investigating further. :-)

Just to make sure this wasn't caused by excessive network traffic / load, I've run this:
curl.curl http://cloud-images.ubuntu.com/xenial/current/xenial-server-cloudimg-amd64-disk1.img > foo
successfully in the virsh vm at ~5.4 MB/s.

Cheers,
- Loïc